Horizontal revolute robot

ABSTRACT

In a horizontal revolute robot, an upper end of a ball screw (21) of a direct-acting actuator (100) is rotatably supported by a top plate of a column (10), and the lower end thereof is coupled to a drive unit (40) disposed on a base plate of the column. A first link (220) is pivotally coupled to a coupling member (210) of a manipulator (200) fixed to a slider (30) of the actuator, and a second link (240) is pivotally coupled to the first link. The ball screw is rotated by the drive unit to move the manipulator along the ball screw in unison with the slider, and servomotors (230, 250) of the manipulator are driven to turn both the links within a horizontal plane, so that a wrist portion of the robot is positioned in a robot installation space for robot operation. Since no base is required to turnably support the actuator, the robot is small-sized, light in weight, and low-priced. Since the lower movement limit position of the manipulator is low, the range of action of the robot is wide.

BACKGROUND OF THE INVENTION Technical Field

1. Field of the Invention:

The present invention relates to a horizontal revolute robotsmall-sized, light in weight, enjoying a wide range of action, andlow-priced.

2. Description of the Related Art:

It is generally known to employ a cylindrical coordinate robot formaterial handling, transportation of heavy objects, etc. The cylindricalcoordinate robot, having a first direct-acting or prismatic actuatordisposed on a base for swivel motion and extending vertically of therobot and a second direct-acting actuator extending horizontally, isarranged to move the second actuator in the vertical direction by meansof the first actuator, and drive an arm in the horizontal direction bythe second actuator, so as to permit an end effector attached to the armto perform various operations. Thus, the cylindrical coordinate robothas advantages such as high repeatability. However, the base thereof islarge-sized, and the first actuator must be coupled to a drive mechanismaccomodated in the base, so that the assembly, maintenance, andtransportation of the robot require much labor, thus entailing highercosts, and requiring a wide robot installation space. Also, since thelower movement limit position of the second actuator is high, the rangeof action of the robot is narrow.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a horizontal revoluterobot which eliminates the aforementioned drawbacks of the conventionalcylindrical coordinate robot, which is small-sized and light in weight,has a wide range of action, and permits reduction in costs ofmanufacture, assembly, maintenance, and transportation.

In order to achieve the above and other objects, a horizontal revoluterobot according to the present invention comprises a direct-actingactuator and a manipulator including at least one horizontal revolutejoint and arranged for swivel motion within a horizontal plane. Thedirect-acting actuator includes a feed screw extending vertically of therobot, a column including an upper plate member rotatably supporting thefeed screw at an upper end of the feed screw and a lower plate memberspaced vertically of the robot from the upper plate member, a drive unitdisposed on the lower plate member and coupled to a lower end of thefeed screw for rotating the feed screw, and a slider coupled to the feedscrew and movable along the feed screw with rotation of the feed screw.The manipulator is coupled at its proximal end portion to the slider soas to be movable in unison therewith vertically of the robot.

According to the present invention, as described above, the manipulatorswivelable within a horizontal plane is vertically movable in unisonwith the slider of the direct-acting actuator, so that there is no needof elements which correspond to the large-sized base and the drivemechanism accommodated therein of the conventional cylindricalcoordinate robot. As a result, the robot can be made compact in size,light in weight, and simple in construction. Thus, the assembly,disassembly, and transportation of the robot are facilitated, costs ofmanufacture, assembly, maintenance, and transportation can be reduced,and the reliability can be improved. Further, there is no need of a widerobot installation space. Furthermore, the lower movement limit positionof the manipulator is low, so that the range of action of the robot iswide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing a horizontal revoluterobot according to one embodiment of the present invention;

FIG. 2 is a schematic perspective view showing a direct-acting actuatorof the FIG. 1 embodiment;

FIG. 3 is a schematic plan view of the directacting actuator taken alongline III--III of FIG. 2;

FIG. 4 is a schematic perspective view showing a conventionalcylindrical coordinate robot;

FIG. 5 is a schematic perspective view showing another conventionalcylindrical coordinate robot, and

FIG. 6 is a plan view of the ball nut mounting plate of the robot ofFIG. 1 with all other components removed for clarity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 4 and 5, a conventional cylindrical coordinaterobot will be described in brief.

The conventional cylindrical coordinate robot comprises a base 1, afirst direct-acting actuator 2 disposed on the base for swivel motion,and a second actuator 3 driven vertically by the foregoing actuator. Thefirst actuator 2 is turned around a swivel axis (θ-axis) by means of adrive mechanism accommodated in the base 1 so that a feed screw 2a ofthe first actuator 2 is rotated to move the second actuator 3 along afirst translation axis (Z-axis), and an arm 3a is driven along a secondtranslation axis (R-axis) by means of the second actuator 2. In thedrawings, symbols α, β and γ designate swivel axes of a wrist portionattached to the distal end of the arm 3a.

The base 1 must have a mechanical strength high enough to support thefirst and second actuators 2 and 3, an object to be transported, etc.,and should be able to contain the drive mechanism, so that its externaldimensions and weight are substantial. Further, it is necessary tosupport the feed screw 2a of the first actuator for rotation by means ofthe base 1, and couple the screw and the drive mechanism to each other.Consequently, a wide robot installation space is needed, and theassembly, maintenance, and transportation of the robot require muchlabor, so that the cost increases. Since the lower movement limitposition of the second actuator 3 is high, moreover, it is difficult tomove the arm 3a close to the floor surface, and the range of action ofthe robot is narrow.

Referring to FIG. 1, a horizontal revolute (jointed cylindricalcoordinate) robot, according to one embodiment of the present invention,is arranged to perform transportation operations, for example. The robotcomprises a direct-acting or prismatic actuator 100 and aseries-connected manipulator 200 arranged to be moved vertically of therobot by means of the actuator. The actuator 100 is so arranged as tocause a slider 30 to reciprocate along a feed screw 21 of a feed screwunit 20 supported by a column 10 when a drive unit 40 is operated,thereby causing the direct-acting manipulator 200 whose proximal endportion is coupled to the slider 30 to reciprocate vertically of therobot.

The direct-acting manipulator 200 includes a coupling member 210 whichis fixed to the upper surface of the slider 30 of the direct-actingactuator 100 so as to be movable in unison with the slider. A first link220 is coupled at its coupling portion (first horizontal revolute joint)221 to the distal end of the coupling member 210 so as to be rotatablerelatively to the coupling member 210, the coupling portion beingprovided at the inner end of the link 220. Also, a first servomotor 230,which is used to change the operative position of the first horizontalrevolute joint, that is, to turn the first link 220 within a horizontalplane around a first swivel axis of the robot extending at right anglesto the first horizontal revolute joint, is fixed to the coupling member210 or the slider 30 by the use of a suitable means (not shown).Further, a second link 240 is coupled, at one end thereof, to a couplingportion (second horizontal revolute joint) 222 at the outer end of thefirst link 220 so as to be rotatable relative to the first link 220.Also, a second servomotor 250 for swiveling the second link 240 within ahorizontal plane around a second swivel axis of the robot extending atright angles to the second horizontal revolute joint, is fixed to thefirst link 220 by the use of a suitable means (not shown). Moreover, awrist portion (not shown) of the manipulator 200 is attached to thedistal end of the second link 240, and an end effector (robot hand fortransportation in the present embodiment, not shown) for variousoperations is attached to the wrist portion. Reference numeral 260denotes a servomotor for controlling the posture of the wrist portion.Other servomotors for wrist portion posture control and a drivemechanism for opening and closing the robot hand are not shown.

Referring to FIGS. 2 and 3, the column 10 of the direct-acting actuator100 has a pair of end walls 11 which extend parallel to a translationaxis 300 of the robot and are spaced from each other. The upper andlower ends of each end wall 11 are fixed to a top plate 12 and a baseplate 13, respectively. For example, each end wall 11 is formed ofchannel steel, and the top and base plates 12 and 13 are each formed ofa steel plate. These elements 11 to 13 are welded to one another attheir junctions, so that the column 10 is solid as a whole. The endwalls 11 and the top and base plates 12 and 13 have their respectiverequired thicknesses for mechanical strength high enough to bear thewhole robot and an object to be transported. Front and rear covers 15and 16 (FIG. 3) are disposed on the side facing the slider 30 of thecolumn 10 and on the side away from the slider, respectively. These twocovers cooperate with the end walls 11 to define a space in which thefeed screw 21 and various elements mentioned later are housed.

A servomotor 41 is fixed to the upper surface of the base plate 13, andits output shaft (not shown) is coupled to the input side of a reductiongear (not shown) accommodated in a gear box 42 which is fixed to theupper surface of the base plate 13 by means of, e.g., bolts. Theservomotor 41 cooperates with the reduction gear to constitute the driveunit 40 for the translation axis 300. The servomotor 41, along with theservomotors 230, 250 and 260 of the manipulator 200, internal measuringsensors of the actuator 100, and internal sensors (not shown) of themanipulator 200, are connected to a numerical control unit (not shown)for controlling the drive of the servomotors, by means of a cable group51 (FIG. 3) supported by cable receiving hardware 50 which is fixed tothe slider 30.

The feed screw unit 20 includes the feed screw preferably formed of theball screw 21. A bearing unit 22, which supports the ball screw 21 in amanner permitting relative rotation and preventing relative axialmovement, is attached to the upper end of the ball screw 21. The bearingunit 22 is removably fitted in a notch 12a which is formed in the sideedge of the top plate 12 of the column 10 on the side facing the slider30, so as to be in alignment with the translation axis 300 and extendthrough the top plate 12. The outer end of the notch 12a opens to theend face of the top plate 12 on the side facing the slider 30 so thatthe ball screw 21 can pass through the notch 12a. The lower end of theball screw 21 is removably coupled to the reduction gear accommodated inthe gear box 42.

The slider 30 includes a main body portion 31 which is integrally formedat its lower part with a pair of guide members 32 protruding outwardlyfrom the opposite sides of the slider body 31. These guide members 32are individually slidably engaged with a pair of guide rails 14 whichare fixed individually to the end faces of the paired end walls 11 ofthe column 10 on the side facing the slider 30. Further, a plate member33, projecting toward the ball screw 21 and extending traversely of theball screw 21, is formed at the lower part of the slider body portion 31integrally therewith. A notch 31a similar to the notch 12a is formed atthe distal end edge of the plate member 33 on the side facing the ballscrew 21, and its end opens to the end face of the plate member 33 onthe side facing the ball screw 21. The slider 30 further includes a ballnut 34 which is threadedly engaged with the ball screw 21, and the ballnut 34 is fixed to the plate member 33 in a manner such that it isfitted in the notch of the plate member 33. Numeral 35 (FIG. 3) denotesa seal member which, fitted on each side face of the slider body 31, isslidable relatively to the front cover 15 of the column 10.

In the following, procedures of assembling the robot constructed abovewill be explained.

After the drive unit 40 is first disposed on the base plate 13 of thecolumn 10, the guide members 32 are fitted individually on the guiderails 14, and the slider 30, previously fixedly fitted with the cablegroup 51 by means of the cable receiving hardware 50, is mounted on thecolumn 10. Subsequently, the ball nut 34 is engaged with the ball screw21, and the bearing unit 22 is mounted to the upper end of the ballscrew 21. Then, the lower end portion of the ball screw 21 is diagonallyinserted into the internal space of the column 10, and the ball screw 21is then set upright so that the lower end portion of the ball screw 21is fitted in the notch of the plate member 33 of the slider 30, and thatthe upper end portion of the ball screw 21 is fitted in the notch 12a ofthe top plate 12 of the column 10. Then, the lower end of the ball screw21 is coupled to the reduction gear in the gear box 42 from above. Then,the bearing unit 22 is fixed to the top plate 12 in a manner such thatit is fitted in the notch 12a. Subsequently, the ball nut 34 is fixed tothe plate member 33, with the same nut fitted in the notch. Further, thefront and rear covers 15 and 16 and the like are mounted, whereuponassembling the direct-acting actuator 100 is completed. In this manner,the feed screw 21 can be mounted from the slider side of the column 10,so that the actuator 100 can be assembled quickly and safely even in anarrow working space. Thereafter, the coupling member 210 of themanipulator 200 is fixed to the slider 30, the first and second links220 and 240 are further coupled in succession, and the servomotors 230,250 and 260 are mounted, whereupon assembling the robot is finished.

The operation of the horizontal revolute robot will now be described.

When the robot is operated, in response to a control output suppliedfrom the numerical control unit of the robot, the servomotor 41 rotatesat a required speed in a rotating direction corresponding to the controloutput. The rotary force of the motor is transmitted to the ball screw21 through the reduction gear, thereby rotating the ball screw, so thatthe ball nut 34 in engagement with the ball screw and the slider 30integral therewith are guided along the ball screw 21 by the guide rails14, to ascend or descend smoothly for a required distance, in unisonwith the manipulator 200. Meanwhile, a feedback signal from theassociated internal sensor of the actuator 100, which is indicative ofthe actual moved position of the slider 30 in the height direction ofthe robot, is supplied to the numerical control unit. The numericalcontrol unit performs conventional feedback control, thereby positioningthe slider 30 and the manipulator 200 in required vertical positions.Further, the servomotors 230 and 250 are feedback-controlled in likemanner by the numerical control unit. As a result, the first and secondlinks 220 and 240 of the manipulator 200 rotate through a required anglewithin a horizontal plane, around the first and second pivotal axes,respectively, thereby positioning the wrist portion of the manipulator200 in a required position within a horizontal plane. Then, theservomotor 260 and the like are controlled in like manner, so that theposture of the wrist portion, and hence, that of the robot hand, arecontrolled. After all, the robot hand assumes a required position andposture in the robot installation space. Moreover, since the actuator100 can be moved close to the floor surface on which the robot isinstalled, the range of action of the robot is wide. Further, ifnecessary, the robot hand is controlled to be closed or opened in theconventional manner, thereby grasping or releasing the object to betransported.

The column 10 supports moving parts, such as the slider 30, of theactuator 100 and the manipulator 200 with the aid of the ball screw 21and the top plate 12, and satisfactorily stands various moments that areproduced with the vertical movement of the actuator 100 and the swivelmotion of the manipulator 200. Thus, the column 10 resists variousforces of action acting in the axial direction of the ball screw 21, sothat no special axial forces act on the gear box 42 and the reductiongear accommodated therein. In this respect, the gear box 42 and thereduction gear are made compact in size and light in weight.

The present invention is not limited to the embodiment described above,and various modifications may be made. Although the transportation robothas been described by way of example in the above embodiment, the robotmay be modified so that it can perform any other operations. Althoughthe above described robot is provided with the series-connectedmanipulator including the two horizontal revolute joints, a series- orparallel-connected manipulator may alternatively be used including arequired number of horizontal revolute joints.

We claim:
 1. A horizontal revolute robot, comprising:a direct-actingactuator; and a manipulator including at least one horizontal revolutejoint and arranged for swivel motion within a horizontal plane; saiddirect-acting actuator including: a vertically extending feed screw; acolumn including an upper plate member rotatably supporting said feedscrew at an upper end of said feed screw and a lower plate member spacedvertically from said upper plate member; a drive unit disposed on saidlower plate member and coupled to a lower end of said feed screw forrotatively driving said feed screw; and a slider operatively coupled tosaid feed screw and movable along said feed screw with rotation of saidfeed screw; wherein said manipulator is coupled at its proximal endportion to said slider so as to be movable vertically of the robot inunison with said slider; wherein said slider includes a ball nutmounting plate extending transversely of said ball screw, a bearing unitfor supporting said ball screw for relative rotation being mounted to anupper end of said ball screw, said upper plate member being disposedtransversely of said ball screw and formed with a first notch whichopens to an end face of said upper plate member at a side facing saidslider, said bearing unit being removably fitted in said first notch,said ball nut mounting plate of said slider being formed with a secondnotch which opens to an end face of said ball nut mounting plate at aside facing said ball screw, said ball screw being removably fitted insaid second notch.
 2. A horizontal revolute robot according to claim 1,wherein said feed screw is a ball screw, said slider including a ballnut threadedly engaged with said ball screw.
 3. A horizontal revoluterobot according to claim 1, wherein said manipulator includes link meansand a coupling member constituting said proximal end portion of saidmanipulator and movable in unison with said slider, said link meansbeing coupled to said coupling member for swivel motion relative to saidcoupling member by means of said at least one horizontal revolute jointcorresponding thereto.
 4. A horizontal revolute robot according to claim3, wherein said link means includes a plurality of links, each twoadjacent ones of said plurality of links being coupled to each other forswivel motion by means of said at least one horizontal revolute jointcorresponding thereto.
 5. A horizontal revolute robot according to claim1, wherein said direct-acting actuator includes a pair of verticallydisposed guide rails slidably mounting said slider.